Enhanced 3-D-reconstruction algorithm for C-arm systems suitable for interventional procedures

Increasingly, three-dimensional (3-D) imaging technologies are used in medi cal diagnosis, for therapy planning, and during interventional procedures, We describe the possibilities of fast 3-D-reconstruction of high-contrast o bjects with high spatial resolution from only a small series of two-dimensi onal (2-D) planar radiographs, The special problems arising from the intend ed use of an open, mechanically unstable C-arm system are discussed, For th e description of the irregular sampling geometry, homogeneous coordinates a re used thoroughly. The well-known Feldkamp algorithm is modified to incorp orate corresponding projection matrices without any decomposition into intr insic and extrinsic parameters. Some approximations to speed up the whole r econstruction procedure and the tradeoff between image quality and computat ion time are also considered. Using standard hardware the reconstruction of a 256(3) cube is now possible within a few minutes, a time that is accepta ble during interventions. Examples for cranial vessel imaging from some cli nical test installations will be shown as well as promising results for bon e imaging with a laboratory C-arm system.